This invention relates to means for and method of preparing printing plates having multiple images in an exact relationship to each other.
The object of this invention is to provide means for preparing printing plates in a more economical and more accurate method than has heretofore been possible.
In making printing plates, multiple negatives or positives, the image or images are photographically repeated by the use of a negative or positive contained in the subject, the negative or positive being photographically derived from the original drawing.
In the field of printing, there is a need for what is termed stepping over and up of an image on a sensitized plate or negative-type material to provide multiple images each in the exact relationship to the other images. In this field it is also necessary to prepare more than one plate, negative or positive, with multiple images on each, with each representing a color of a multiple color printing job. In such an instance, the relationship of the images not only for one color but for all colors in the multiple color operation.
If the image is to be stepped horizontally and vertically, it not only must have the holes horizontally as above indicated, but also have sets of holes in proper relationship in a vertical manner. There must be as many sets of holes as there are vertical steps. It is important in stepping vertically and horizontally that holes be in absolute alignment with each other.
Various punching apparatus for punching registration holes have been suggested in the prior art involving, interalia, slideable hole punching means, guide pins and guide straight edges. Punching devices previously suggested, however, have not provided totally suitable overall performance in terms of speed and/or accuracy or being limited in the capability of utilizing only the accurately sized sheet material or of producing accurate punching on only one side of the sheet material.